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[Qemu-devel] [PATCH 05/14] nbd/client: Drop pointless buf variable
From: |
Eric Blake |
Subject: |
[Qemu-devel] [PATCH 05/14] nbd/client: Drop pointless buf variable |
Date: |
Fri, 30 Nov 2018 16:03:34 -0600 |
There's no need to read into a temporary buffer (oversized
since commit 7d3123e1) followed by a byteswap into a uint64_t
to check for a magic number via memcmp(), when the code
immediately below demonstrates reading into the uint64_t then
byteswapping in place and checking for a magic number via
integer math. What's more, having a different error message
when the server's first reply byte is 0 is unusual - it's no
different from any other wrong magic number, and we already
detected short reads.
Signed-off-by: Eric Blake <address@hidden>
---
nbd/nbd-internal.h | 1 +
nbd/client.c | 14 +++-----------
2 files changed, 4 insertions(+), 11 deletions(-)
diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h
index eeff78d3c98..306a533dcd1 100644
--- a/nbd/nbd-internal.h
+++ b/nbd/nbd-internal.h
@@ -46,6 +46,7 @@
/* Size of oldstyle negotiation */
#define NBD_OLDSTYLE_NEGOTIATE_SIZE (8 + 8 + 8 + 4 + 124)
+#define NBD_INIT_MAGIC 0x4e42444d41474943LL
#define NBD_REQUEST_MAGIC 0x25609513
#define NBD_OPTS_MAGIC 0x49484156454F5054LL
#define NBD_CLIENT_MAGIC 0x0000420281861253LL
diff --git a/nbd/client.c b/nbd/client.c
index 0be89f9e641..17ee24492a4 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -731,7 +731,6 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name,
QIOChannel **outioc, NBDExportInfo *info,
Error **errp)
{
- char buf[256];
uint64_t magic;
int rc;
bool zeroes = true;
@@ -752,21 +751,14 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char
*name,
goto fail;
}
- if (nbd_read(ioc, buf, 8, errp) < 0) {
+ if (nbd_read(ioc, &magic, sizeof(magic), errp) < 0) {
error_prepend(errp, "Failed to read data: ");
goto fail;
}
-
- buf[8] = '\0';
- if (strlen(buf) == 0) {
- error_setg(errp, "Server connection closed unexpectedly");
- goto fail;
- }
-
- magic = ldq_be_p(buf);
+ magic = be64_to_cpu(magic);
trace_nbd_receive_negotiate_magic(magic);
- if (memcmp(buf, "NBDMAGIC", 8) != 0) {
+ if (magic != NBD_INIT_MAGIC) {
error_setg(errp, "Invalid magic received");
goto fail;
}
--
2.17.2
- [Qemu-devel] [PATCH for-4.0 00/14] nbd: add qemu-nbd --list, Eric Blake, 2018/11/30
- [Qemu-devel] [PATCH 04/14] qemu-nbd: Simplify --partition handling, Eric Blake, 2018/11/30
- [Qemu-devel] [PATCH 05/14] nbd/client: Drop pointless buf variable,
Eric Blake <=
- [Qemu-devel] [PATCH 01/14] qemu-nbd: Use program name in error messages, Eric Blake, 2018/11/30
- [Qemu-devel] [PATCH 06/14] nbd/client: Move export name into NBDExportInfo, Eric Blake, 2018/11/30
- [Qemu-devel] [PATCH 02/14] nbd/client: More consistent error messages, Eric Blake, 2018/11/30
- [Qemu-devel] [PATCH 03/14] qemu-nbd: Fail earlier for -c/-d on non-linux, Eric Blake, 2018/11/30